1. Field of the Invention
The present invention relates to solid-state image pickup apparatuses and methods, and more particularly, to a solid-state image pickup apparatus that includes analog-to-digital (AD) conversion circuits provided in correspondence with individual columns and that performs arithmetic processing on a plurality of digital signals obtained by the AD conversion circuits and to a method for driving the solid-state image pickup apparatus.
2. Description of the Related Art
In applications requiring high-speed performance for displaying video images or the like, known solid-state image pickup apparatuses that perform a so-called horizontally thinned-out reading are available. More specifically, these solid-state image pickup apparatuses read analog electrical signals, which are obtained by converting incident light at pixels arranged in a matrix, every other column (hereinafter, this type of reading serves as a synonym for a horizontally thinned-out operation).
An image sensor having AD conversion circuits provided in correspondence with individual columns and performing arithmetic processing on digital signals is disclosed in Japanese Patent Laid-Open No. 2006-025189. More specifically, two register circuits are provided for every column of pixels. After two different signal levels of one pixel are stored, the difference between the two different signal levels is calculated in a digital section of the image sensor.
When a horizontally thinned-out operation is performed using the circuit configuration disclosed in Japanese Patent Laid-Open No. 2006-025189, and arithmetic operations are performed on signals stored in a plurality of register circuits, the AD conversion circuits and the register circuits provided for “thinned-out” columns, that is, columns from which signals are not read out, do not contribute to the operation. Thus, in conventional arrangements, there is circuit utilization inefficiency.